1. Field of the Invention
The present invention relates to sensor systems that sense web tension and web movement in processors of photosensitive web.
2. Description of the Prior Art
In photofinishing, it is typical to continuously process long webs of photosensitive material by transporting the web through a series of processing tanks which contain different chemical solutions, and then through a dryer that dries the web. Both photographic film and photographic print paper are commonly processed in this manner.
In the case of photographic film, it is typical to splice together individual strips of undeveloped photographic film for processing. Cine processor machines are used to develop continuously the long web of photographic film formed by splicing the individual strips of film.
In a cine processor, the film web is transported through the tanks by sets of transport rollers on transport racks having an upper set and a lower set of rollers. The film enters the transport rack on one side and is transported in a helical manner between the upper and the lower rollers of the rack until it reaches the outside of the rack where it is transferred to the next transport rack.
As is easily apparent, a malfunction such as a film break results in costly down time and possible damage to the photosensitive film web. The Rawlings U.S. Pat. No. 4,344,073 granted on Aug. 10, 1982 and assigned to the same assignee as the present application, discloses a film break detector in a photographic film dryer. The apparatus disclosed in U.S. Pat. No. 4,344,073 works quite well in detecting a film break in a dryer. However, a further improvement in the art of sensing web breaks in photographic processing equipment would be to forecast such breaks before they occurred and wherein such a system would operate in a dryer or in a chemical tank. Advanced warning of the film breaks would provide the operator with time to correct the problem and avoid possible damage to the photosensitive web.